1. Field of the Invention
The invention relates to a drapery track. More particularly, it relates to an improved drapery track utilizing a "threaded" rod drive means.
2. Brief Description of the Prior Art
Typically, moveable draperies utilize what is referred to in the industry as a "cord track". Such a track allows for the opening and closing of the drapery by means of a cord. One or more pulleys may be utilized with the cord in order to change direction of the force produced by pulling the cord which is attached to a carriage means. The carriage means is caused to traverse along the track support by pulling one or more cords. The carriage means in turn forces a plurality of truck means along the track support, the carriage and the truck means generally being provided with a series of holes into which hooks or pins attached to drapery material may be attached. Such "cord tracks" exhibit several disadvantages. The cords are lengthy, and if allowed to extend below the length of the drape produce a rather unsightly visual effect. The cords may become tangled rendering the drapery track inoperable. Likewise the drapery track operation may be impeded or interrupted by pulling the cord over a sharp or abrasive track surface thus producing fraying and eventual severance of the cord.
Rods providing a spiral threaded drive have been successfully employed in the vertical blind field, thereby allowing for the replacement of the cord and its related mechanism. However, a rod having such a drive means has not been successfully employed in a drapery track. The reason for this inability may be described as follows. The drapery rod if supported only at the rod ends, as is generally the case, deflects due to its weight. Assuming the rod to perform as a simple, uniformly loaded beam, the maximum deflection occurs at the midpoint of the rod, its magnitude being determinable from the following equation: ##EQU1## WHERE W IS THE WEIGHT OF THE ROD, L IS THE ROD LENGTH, E is the modulus of elasticity for the rod and I is the moment of inertia of the rod. (See generally Timoshenko Elements of Strength of Materials, D. Van Nostrand, pp. 197-230 (4th ed. 1962).) It can be seen from the foregoing equation that a change in length produces a corresponding fourth power change in the deflection, i.e. doubling the length of the drapery rod increases the deflection by a factor of 16. As it is often desirable to provide for drapery tracks of great length, such deflections may create substantial problems. When such a rod is rotated within a channel support member, the deflection or "bow" in the rod causes the rod to strike the channel producing unacceptable noise and clatter. Rod supports have been utilized in vertical blinds. However, such supports themselves produce objectionable noise. Moreover, such supports if employed in a drapery track would inhibit the traverse of a carriage drive member which is traversed along the rod when the drapery is opened and closed. Additionally, rods have not been successfully employed in drapery tracks as the drive of such rods may become obstructed by foreign material which may become lodged between the spiral threads. (See generally, Shigley, Theory of Machines, Helical, Worm and Bevel Gears, McGraw Hill pp. 179-206 (1961).
It is an object of this invention to provide an improved rod drapery track. Other and additional objectives will become apparent upon a reading of the entire specification, drawings and claims.